Ballistic converter



UCL 15, 1955 D. T. SIGLEY Erm.

BALLISTIC CONVERTER Filed Sept. 18. 194'?- um .w

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Application September 18, 1947, Serial No. 774,732

Claims. (Cl,l 23S- 61.55

This invention relates to ordnance fire control systems and more particularly to a ballistic computer adapted for use in rate type gyro computer systems for converting director gun orders suitable for guns of a particular size and caliber only into gun orders suitable for guns of other sizes or calibers.

lt has been found desirable, especially in anti-aircraft fire control systems, to incorporate in the lire control director a calculator capable of computing the particular lead angle to the target and of converting this cornputed lead angle into gun orders which are delivered to the elevation and train mechanism of the gun. A limitation imposed upon such a system is that the director can control only guns of a single predetermined ballistic. This invention is directed to the provision of such additional components as will remove the foregoing limitation, the said additional components serving to correct the director gun orders so that they may be suitable for delivery to guns of varying size or caliber.

This invention is predicated mainly upon the discovery that reasonably correct gun orders of a second ballistic may be obtained through the use of certain empirical functions of range to target combined with gun orders of a first ballistic in a relatively simple equation. Electrical values representing these empirical functions of range may be obtained through the electrical loading of potentiometcrs employed in a circuit for controlling the guns cf the second ballistic.

Accordingly, it is a primary object of this invention to incorporate in the rate type gyro computer systems for fire control a calculator that will convert gun orders derived for guns of a first ballistic, into gun orders suitable for guns of a ballistic different from said first ballistic.

it is a further object of this invention to modify gun orders obtained from an electrically operated computer of a director for `guns of predetermined caliber by introducing proper electrical impulses into the output of said computer so as to make its output serve simultaneous ly guns of a caliber different from the said predetermined caliber.

That this invention may be more fully understood, it is described hereinafter as applied to the gun director Marl: 57, to enable the said gun director to supply satisfactory gun orders not only to 5"38 caliber guns for which it is designed but also simultaneously to supply satisfactory gun orders to 40 mm. guns as well. Satisfactory shooting of both 4Q mm. and 5-38 caliber guns from the Mark 57 director' is obtained by Calibrating the Mark 57 director for the 5-38 ballistics and utilizing for the di? mm. ballistics additional components for altering lead angles; e. g., gun orders, in elevation (E) and train (no) according to formulas given in the Equations l and 2 below:

where 2,766,934 Patented Oct. 16, 1956 rice 0g(40)- -gun elevation angle for 40 mm. guns g(40)=gun train angle for 40 mm. guns 0g(5)=gun elevation angle from director system calibrated for 5 "-38 ballistics g(5)=gun train angle from the director system calibrated for "-38 ballistics 1.(R):an empirical function of present range fz(R)=an empirical function of present range E( 5) :output of the elevation gyro servo with the director system calibrated for 5-38 ballistics A(5)=train lead angle from the director system calibrated for 5-38 ballistics An embodiment of the invention Vis described herein and illustrated in the accompanying drawing, wherein:

Fig. l is a block diagram showing the general nature of the units and their connections;

Fig. 2 is a circuit diagram, showing the elevation units; and

Fig. 3 is a circuit diagram, showing the train unit.

Referring firs-t to Fig. l, the director stand 1 has the four outputs of its synchro generators. 36 0p and 2 0p in elevation and 36 op and op in train, fed into the computer 2 as shown. The Outputs 36 0g (5) and 2 0g(5) are the elevation orders for the 5" gun` indicated at 3, the train orders being the outputs 36 g(5) and g(5). The above constitutes the normal setup for the director and the 5" gun and is in itself complete for control of said gun by the directo-r. The prefixes 2 and 36 associated with the various gun orders represent the gear ratios between the gun mount and synchro generators and consequently indicate coa-rse and fine controls respectively. U. S. Patent No. 2,499,970 to Agins sets forth the advantages of such a system.

ln order to control a gun of another size, say 40 mm., simultaneously with the 5" gun, the ballistic converter 4 is necessary. This is a device which will receive as its input-s the same electrical impulses as those delivered to the 5l gunl 3, and further sets of impulses AMS) and 15(5), also derived from the computer 2, these are inherently present within the computer, but normally do not leave it. When needed, however, they may easily be piped out and from such inputs will derive `the proper impulses 36 @(40) and 2 51;(40) to controlV the 40 mm. gun 5 in elevation and 36 @(40) and @(40) to control it in train.

This ballistic converter 4 will now be described in detail, with reference to Figs. 2 and 3 of the drawing. lnasrnuch as Figs. 2 and 3 are identical as to mechanical structure and nearly identical in circuit connections, and differ only in adjustments and values of certainV constants, one description will be sufficient for an understanding of both. lt will be understood, of course, that since Fig. 2 refers to the elevation unit, while Fig. 3 discloses the train unit, necessarily the inputs will vary according to their respective functions, and consequently also their outputs.

Each comprises two input transformers 6 and 7, each transformer 6 being a ll5 volt step-down device, fed from power mains. The transformer 7 in Figure 2 is fed from the elevation Variac in the computer 2, while the transformer 7 in Figure 3 is fed from the train lead angle Variac in said computer.

An intermediate tap 8 (not necessarily or usually a center tap) of the secondary of each transformer 6, is connected by a conductor 9 to a contact R, slidable relatively along a corresponding voltage-dividing potentiometer 10. The relative position of contact R in each case is controlled by the radar and is therefore range-contuolled Since the potentiometer 10 in Figures 2 and 3 is loaded differently, each voltage derived therefrom is range-controlled but is varied at a corresponding desired rate clepending upon the particular empirical function of the range. It will be understood that by appropriate mechanical or electrical changes, the rate of variation of voltage provided by either potentiometer may be modified as desired. For example, the loading in Figure 2 may be produced by grounding a point between the, usually different, resistors 29 and 30 of suitable values through wires 13 and 21 and additionally providing a resistor 3l connected as shown, while similar means, but omitting such eXtra resistor 31, are used in Figure 3. The magnitudes of the resistances of resistors 29, 30 and 31 will determine the nature of the non-linearity produced, and also the point at which such non-linearity begins. Additional resistors, connected in parallel or series or both, with the potentiometers, may also be provided to modify the loading" as may be found necessary or desirable.

Another potentiometer 11 having a slidable contact l2 thereon is connected across the secondary of each trans former 6 as shown. This is for the purpose of balancing the voltage between R and the grounded wire 13 in each case, that is, each slider 12 will be moved, by means de scribed later, to a position where the difference of potential between 12 and R becomes zero. lt will be understood that while for simplicity of' illustration the contacts are shown as slidable, in actual practice the potentiometer is usually constructed with a resistor that rotates about a center, with a stationary contact resting on the outside of the resistor.

This difference of potential is usually relatively small, that is, wires 2S and 13 never have a great voltage between them. As this voltage is relied on for adjusting the slider 12 to balancing position, use is made of the amplifier 14 to increase the voltage to a value sufficient to operate the small motor l5.

The motor 15 is a two-phase alternating current motor, the output of amplifier 14 supplying one phase to winding 16, while the other winding 17 is supplied from the mains, usually through `a resistor or other control means to supply correct voltage thereto. The amplifier 14 is of the resistance-capacity type, and delivers an output current which is substantially 90 degrees out of phase with the input, hence said output is suitable for use as the second phase of the motor supply. The 90 degree phase shift may be obtained in any conventional manner. If desired, an arrangement such as is disclosed in U. S. Patent 2,630,558 to Arsem et al. may be employed to shift the phase of the voltage applied to amplilier 14 and thereby provide the proper output.

Because of the amplification, the slight differences of potential between wires 21 and 28 are so magnified that even a very small voltage will cause the motor 15 to run until the slider l2 has been restored to practically the null position, thus giving a very sensitive adjustment. It should also be noted that whenever the polarity of 12 to 13 changes, the output of amplifier 14 will shift 180, that is, it will reverse in relative polarity, thus reversing one phase of the motor 15 and causing its rotation to reverse in direction.

Since motor 15 has inertia, and would cause the adjustment of slider 12 to overshoot the null position due to its momentum, producing hunting, suitable damping means are provided to prevent such action. This damping device consists of a damping generator 18 of the type more fully described on pages 28 and 29 in OP1323A Gun Fire Control System Mk 57, an unclassified publication of the U. S. Navy Bureau of Ordnance. One winding 19 is traversed by a current derived from the input current supplied to the amplier 14, as modified by the shunting resistor 22, which is connected in parallel with winding 19, thus controlling the `amount of feed-back. This will be substantially either in phase, or of' 180 phase shift with respect to the current liowing in the other winding 20, which is fed directly from the secondary winding 26 of transformer 6, thus controlling the damping in the proper sense.

Mechanical connections are provided, as shown by the dashed lines, between the motor 15, the generator 18, and

the slider 12 as well as the two differential synchro generators, 23 and 24 of Figure 2 or 23 and 25 of Figure 3. lt will be understood that suitable gearing ordinarily will be included in these various mechanical connections, to provide the correct relative speeds of the various elements.

ln Figure 2, the differential generators 23 and 24 are supplied with the input impulses 36 0g(5) and 2 08(5), respectively, while they are simultaneously mechanically affected by the rotations supplied from the motor l5, whereby the outputs 36 0,;(40) and 2 6g(40) are derived from the said inputs.

ln Figure 3, the differential generators 23 and 25 are supplied with the input impulses 36 g(5) and g(5), respectively, while they are simultaneously mechanically atected by the rotations supplied from motor 15, whereby the outputs 36 g(40) and g(40) are derived from the said inputs.

The synchro generator outputs in Figure 2 are thus the correct 40 mm. gun elevation orders, while those of Figure 3 are the correct 40 mm. gun train orders.

It should be understood that while specific sizes of guns have been mentioned in describing the invention, these are purely illustrative and may be reversed or otherwise varied at will. For example, impulses derived from a 40 mm. director could equally well be used to actuate a director for a 5" gun. Nor is the invention limited to the simultaneous directing of only two gun sizes, but on the contrary three or more sizes may be directed simultaneously by a single director, with a suitable ballistic converter.

It should also be kept in mind that while specific arrangements of resistors have been disclosed as potentiometer loading means, many modified connections may also be employed. Knowing what non-linearity is required, it becomes a mere mathematical problem to design suitable resistor systems to put in parallel or series, or otherwise, in circuit with any given potentiometers to provide the desired deviation from linearity. The term loading is used to designate such modification of the normally linear variation of resistance of a potentiometer.

Having now described our invention, what we claim as new is:

l. In combination with a computer providing electrical train and elevation orders for a first type of gun, a ballistic converter comprising, a first non-linear potentiometer to receive the electrical train order for the first type gun, a second non-linear potentiometer to receive the electrical elevation order for said first type gun, said first and second potentiometers modifying the orders to said first type of gun in accordance with the target range and the non-linear characteristics of said potentiometers, and means receiving said modified gun orders for controlling a second type gun in train and elevation.

2. A ballistic converter as claimed in claim 1 wherein said last named means includes a motor providing a r0- tational displacement proportional to said modified gun orders and a differential generator connected to said motor for transmitting said rotational displacement to said second type gun.

3. In combination with a computer providing train and elevation orders for a first type of gun, a ballistic converter comprising, a non-linear potentiometer including a movable contact, said potentiometer being energized by one of the electrical orders from the computer, said movable contact being positioned in accordance with the range of a target from the gunsite, a balancing potentiometer including a movable contact, a source of constant potential for energizing said balancing potentiometer, an amplifier receiving the difference between the potential at said movable contact of said balancing potentiometer and the potential at said movable contact of said nonlinear potentiometer, a motor mechanically connected to said balancing potentiometer contact to move said contact, said motor being energized by the output of said amplifier thereby providing an amount of motor rotation gun order being applied to said input winding and said motor rotation being applied to said generator rotor.

5. In combination, a gun director providing target elevation information 0p and target train information op, a computer for modifying said target informations to provide an elevation order 6g(5) for a first type (5) gun and a train order g(5) for said iirst type gun, and a ballistic converter receiving said first type gun orders and modifying the same to provide an elevation order 0;(40) and a train order @(40) for a second type (40) gun, said ballistic converter comprising, a potentiometer including a movable contact and having a non-linear resistance variation f1(R) with movement of said movable contact, the movement of said movable contact being in accordance with target range (R), means for applying to said potentiometer the electrical elevation order (E) corresponding to said elevation gun order 0g(5), means providing a rotational displacement f1(R)E(5) proportional to the potential at said potentiometer movable contact, and a differential generator for combining said rotational displacement fi(R)E(5) with said elevation order 61;(5) for said first type gun thereby providing said elevation order 0g(40) for said second type gun.

References Cited in the tile of this patent UNITED STATES PATENTS 

